Random Response Analysis on Large Models

Steve Bell_21840
Steve Bell_21840 New Altair Community Member
edited April 2022 in Community Q&A

Hi,

 

We are developing some large FE models, in excess of 4 million elements. Which must

be subjected to a series of random vibration analyses. Have there been any developments

or tips for keeping the huge temporary files created by Optistruct to a minimum. It appears

we are restricted to only creating results for sets, which means re-running the analyses

several times on the same model.

Note:

  1. We do ensure no results are created for the frequency response sub-step.
  2. We have to use a 1Hz increment for the random vibration analysis.
  3. The frequency range is also large typically 5 to 1000Hz.
  4. We are exceeding 4tb of discuss space.

 

Kind regards,

 

Steve

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Answers

  • Adriano A. Koga
    Adriano A. Koga
    Altair Employee
    edited April 2022

    it seems indeed a large problem to solve.

     

    Is it possible to break into smaller frequency intervals? instead of running it from 5 to 1000Hz directly.

    You can use EIGSAVE and EIGRETRIEVE to avoid running the normal modes everytime.

     

    Also, instead of using FREQ1 with 1Hz interval, what about reducing FREQ1 interval, but using FREQ4 to get a better frequency interval close to your ressonant modes? (if not so many)

  • Xiaolei
    Xiaolei
    Altair Employee
    edited April 2022

    Hi @Adriano A. Koga I work with @Steve Bell on this in a Support ticket. 

    So I copy my finding here::)

    • As far as I know the analysis was set up in good practice.
    • In 2021 version, it takes much less disk space-228G. While in 2020 version, it needs 1.4TB. Results are the same. 
    • Run time using 16 cpu:
      • 2021: 100 minutes
      • 2020: 127 minutes

    So we suggested to use 2021 or 2022 in the future as they have be enhanced. 

    Thanks. 

    Xiaolei

     

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